Sabot projectile with core guiding means



June 3, 1969 w. ENGEL 1 SABQT PROJECTILE WITH CORE GUIDING MEANS FiledSept. 5, 1967 2 i 1 2 .5 m 5 w. i5 I M W \w t 3 l 7 Ina/ll .9 W W 8 7 Hl\\\ 2 R. 2 H 1 M 0 I I h w w Il 2 I 3 m T U .6 a 6 a o u 8 w H B w 9 72 1 5 2 United States Patent US. Cl. l02-93 2 Claims ABSTRACT OF THEDISCLOSURE In a sabot projectile the sabot is provided with a drillingin which the subcalibre core is guided during emergence from the sabot.This subcalibre core has a tail portion which is seperated from thecentre section of the core by an annular groove, the tail portion beinglocated within a spherical zone the radius of which is equal to theradius of the sabot drilling. The tail portion has at leastapproximately the same diameter as the centre section of the subcalibrecore, as a result of which canting and jamming of the subcalibre core onemerging from the sabot are obviated.

The present invention relates to a sabot projectile and in particular toa sabot projectile embodying a sabot with a drilling in which asubcalibre core is guided during emergence from the sabot.

The object of the invention is to produce a sabot projectile in whichcanting and jamming of the subcalibre core on exit from the sabot areobviated.

The invention has as a further object the production of a sabotprojectile in which the emergence of the subcalibre core from the sabotis facilitated.

An additional object of the invention is the production of a sabotprojectile in which the tail portion of the subcalibre core is so formedthat complete exit of the subcalibre core from the sabot is assured.

The drawing illustrates two examples of execution of the subject of thepresent invention:

FIG. 1 shows a longitudinal section through a first example of executionof the sabot projectile,

'FIG. 2 shows a view of the rearward portion of the subcalibre core inaccordance with a second version of the execution of the sabotprojectile, and

FIG. 3 shows a view of the rearward portion of the subcalibre core as itemerges from the sabot.

In accordance with FIG. 1 a sabot 1 encloses a subcalibre core 2. Untilfiring the sabot 1, manufactured in the form of a sleeve of an aluminiumalloy or some other light metal, has its rearward portion located in theconventional manner in the mouth of a cartridge case not illustrated. Onthe sabot 1 is mounted a rotating band (driving band) 3 which transfersthe torsional momentum from the grooves in the bore of the weapon, notillustrated, to the sabot 1 and which is made of steel. A furthersimilar rotating band (driving band) 4 is located at the forepart of thesabot 1. In order to save weight that portion of the sabot 1 situatedbetween the two rotating bands (driving bands) 3 and 4 has been given asmaller external diameter than the tail portion.

A cylindrical drilling 5 at the front of the sabot 1 serves to centreand guide the subcalibre core 2. This drilling 5, which is anodised bythe Ematal process and then barrel burnished, opens into a coaxialdrilling 7 of larger diameter machined into the tail of the sabot 1 andthreaded as to its rearward portion. The transition from drilling 5 todrilling 7 takes the form of a shoulder 6. In the aforementioned threadof the sabot a solid piece 8 with a depression 9 in its forward face islocated by screwing. This depression '9 is surrounded by an annularsurface 3,447,466 Patented June 3, 1969 10 against which the tailsurface of the subcalibre core 2 is braced. In the annular cavity 11delimited by the shoulder 6 and the forward face of the screwed piece 8are the orifices of two drillings 12 which penetrate the wall of thesabot 1.

It is advisable for the subcalibre core 2 to be made partly or wholly oftungsten carbide and to be provided with a cylindrical centre sectionwhich culminates in an ogive 13 in front and has a tail portion 14.Borne between the centre section and the tail portion 14 in an annulargroove 15 machined into the subcalibre core is an annular safety element16 in the form of a holding device with a rectangular cross-sectionwhich is provided with a slit 18 the outer surface of which is numbered17. This safety element 16, which projects beyond the tail portion 14and is capable of being expanded under the influence of centrifugalforce, is located between the shoulder 6 of the sabot 1 and the groovedwall arranged perpendicular to the axis of the projectile as the rearsupporting surface of the subcalibre core 2.

As shown in FIG. 1, a forward zone 19 of the tail portion 14 of thesubcalibre core limited by the rear grooved wall 26 is formed by atruncated cone expanding towards the rear. A further cylindrical piece21 adjoining the aforementioned truncated cone 19 at the rear andhereinafter referred to as the guide zone has an equal diameter to thecentre section but in relation to the drilling 5 in the sabot 1 has asmall amount of play which may for example amount to 0.03 mm. Takingaccount of the aforesaid small amount of play, the height of this guidezone 21 is determined by the requirement that the tail portion 14 of thesubcalibre core 2 be able to rotate in the drilling 5 about the forwardedge 24 of the zone 21, i.e. by an angle corresponding to the maximumangle of pitch occurring in the subcalibre core 2. Thus the tail portionmust be located within a spherical zone the radius R of which is equalto the radius of the drilling 5 of the sabot 1 and with approximatelythe same diameter as the centre section of the subcalibre core. Thethird zone forming the rear end of the tail portion 14 is a truncatedcone 22 which tapers towards the rear from the diameter of the guidezone 21. The generatrices of the said truncated cone form an angle withthe base surface 27 which is greater than for example in order toobviate material crumbling away along the periphery of the base surface27 under the heavy pressure loadings of firing.

The generatrices of the truncated cone 19 coincide with straight lineswhich connect the leading edge 24 'of the cylindrical guide zone 21 withthe interior edge of the grooved wall 25 laid out transverse to the axisof the projectile and limiting the annular groove at the front. Thesesraight lines form with the axis of the projectile an angle which is atleast as large as the maximum angle of pitch the subcalibre core 2 cantake up on emerging from the sabot 1.

The second execution version of a subcalibre core 2 as illustrated inFIG. 2 is distinguished from the example illustrated in FIG. 1 by thefact that the guide zone 20 reaches as far as the annular groove 15 andis formed by a zone of a sphere. The largest cross-section of thespherical zone 20 aligned perpendicular to the axis of the projectileand parallel to a terminal surface displays a diameter which correspondsto the diameter of the sphere and therefore to the diameter of thecentre section of the subcalibre core 2. A tangential surface laid outat the leading edge 28 of the spherical zone 20, which forms with theaxis of the projectile an angle at least equal to the angle of pitch ofthe subcalibre core, touches the interior edge of the transverse surface25 limiting the annular groove 15 at the front.

Before the subcalibre core 2 is mounted in the sabot 1 it is processedas follows:

After microfinish grinding and degreasing of the cylindrical outersurface it is coated by spraying with a layer consisting of a mixture of9.1% (parts by weight) of molybdenum disulphide M08 7.6% phenol resin(binding agent) and 83.3% ethyl acetate (solvent and thinner).

This layer, which adheres to the outer surface to a thickness of 1.5 to2, 0.10- mm., is then lightly polished after which the subcalibre coreis heated and held at a temperature of 80 to 100 degrees centigrade forat least 2 minutes. During this period the solvent and thinner agentevaporates so that finally a dry lubrication film consisting of M05 isleft adhering to the subcalibre core. The composition of this film willnot alter even during years of shelf life.

The method of operation of the sabot projectile described follows fromthe construction:

After ignition of the propellant charge the sabot projectile acceleratesrapidly in the bore and the subcalibre core 2 is pressed against thebearing surface and compresses, i.e. plastically deforms it. In relationto the sabot 1 the subcalibre core 2 thus moves to the rear and thisreleases the grip of the safety element 16.

On axial acceleration by the subcalibre core 2 the safety element 16 ispressed against the rear grooved wall and is itself set in rotation bythe frictional force that is thus generated, so that even before thesabot projectile leaves the bore of the weapon the safety elementexpands under the influence of the centrifugal force acting upon it,moves completely free of the annular groove and positions itself in thebuffer chamber 11 with its outer surface 17 against the inner surface ofthe drilling 7.

After emergence of the sabot projectile from the bore of the weapon, thesabot 1 is by reason of its large leading surface more heavilydecelerated than the subcalibre core 2 so that the latter moves forwardin relation to the sabot 1, i.e. overruns it, and by reason of the lowlevel of friction to be overcome by the subcalibre core 2 with itscoating of lubricating film when moving within the drilling 5 of thesabot 1 this overrunning effect is almost Without impediment.

When the centre section of the subcalibre core 2, which is locatedforward of the annular groove 15, emerges from the drilling 5 of thesabot 1 and is no longer guided therein, it is impossible for canting orjamming symptomised by heavy resistance to movement to occur should thesubcalibre core 2 be subjected to forces operating transversally to itsaxis. On the contrary, the subcalibre core 2 is able under the influenceof these transversally acting forces to take up an attitude in which itforms with the axis of the sabot drilling an angle corresponding to itsmaximum pitch angle (see FIG. 3). At the time, in the versionillustrated in FIG. 1 the truncated cone forming the leading zone 19 ofthe tail portion of the subcalibre core 2 is able to position itselfagainst the wall of the sabot drilling 5 and slip along it in a forwarddirection without any diametrically adjacent portion of the tail portion14 touching the wall of the drilling 5. With the version of thesubcalibre core 2 illustrated in FIG. 2 the spherical guide zone 20 actsas an articulation preventing jamming.

The size of the distance between the rearward end of the centre sectionof the subcalibre core 2 and the guide zones 21 and 20, or between theedges 23 and 24 (FIG. 1), or between the edge 23 and the greatestdiameter of the spherical zone 20, designated 29 (FIG. 2), conditionsthe size of the bearing forces transmitted to the subcalibre core 2 bythe wall of the drilling 5, forces which are generated when forcesacting transversely to the subcalibre core 2 affect it. By properlyselecting this distance the facility is obtained to influence favourablythe frictional resistance forces generated by these bearing forces.

I claim:

1. Sabot projectile with a subcalibre core embodying a cylindricalcentre section, a tail portion and an annular groove between these twoparts, and a sabot having a cylindrical drilling in which the subcalibrecore is guided during emergence from the sabot, the tail portion of saidsubcalibre core has a section tapering towards the front in the form ofa spherical zone, this zone having a diameter which is at leastapproximately equal to the diameter of the cylindrical centre section ofthe subcalibre core.

2. Sabot projectile in accordance with claim 1 with a film of drylubricating agent covering the subcalibre core and with an anodized andburnished bore in the aluminium alloy sabot.

References Cited UNITED STATES PATENTS 405,690 6/1889 Ball .102-933,359,905 12/1967 Engel 10293 FOREIGN PATENTS 8/1919 Great Britain.

OTHER REFERENCES BENJAMIN A. BORCHELT, Primary Examiner.

JAMES FOX, Assistant Examiner.

